The present invention relates to wireless communication systems and, more particularly, to a method and apparatus capable of effectively handling reports signaling a channel quality indicator, a precoding matrix indicator, and/or a rank indicator in a wireless communication system having carrier aggregation.
The desire for high data rates in wireless communication systems has steadily increased. Accordingly, the complexity of the wireless communication systems has also increased. Communication from a base station, or node B, to a mobile device, or user equipment, is termed downlink communication, and communication from the user equipment to the node B is termed uplink communication. To provide more efficient communication, reference signals may be transmitted downlink from the node B to the user equipment in a radio channel. The user equipment analyzes the signal it receives to measure characteristics of the channel, and the user equipment transmits an indication of the downlink characteristics (often termed a channel quality indicator or CQI) from the user equipment to the node B. In a basic form, the CQI indicates the characteristics, such as the signal to noise ratio, of a single channel over frequency. The node B in turn may modify, based on the CQI from the user equipment, how it transmits downlink in order to more effectively communicate.
Higher speed wireless communication systems use multiple-input multiple-output (MIMO) technology where both node B and user equipment have multiple antennas. Accordingly, there are multiple channels between the node B and the user equipment: one for each combination of node B antenna and user equipment antenna. Thus, the user equipment may transmit increased information to indicate the increased variety of communication characteristics that may occur.
Still higher speed wireless communication systems add carrier aggregation technology where multiple component carriers are combined to transmit data between the user equipment and node B. This increases the amount of possible communication characteristics. Additionally, the component carriers may differ for downlink and uplink communication and may change dynamically. Thus, it may be difficult to supply current measurement results of the communication characteristics without impacting communication of user data.